Depends. Low BP requiring treatment is vanishingly rare in the UK - common in the US because they're all private so if your doc gives you meds then s/he gets cash! Over here we only treat low BP if it's really low, or giving you probs. Would need more info before making a pronouncement.
The man with Hypertension has no difference in errectile function than a man with typotension, the factors that affect errectile dysfunction are many and varied:
Recent sexual experience (got leg/hand friendly over within last 10 mins...how porn 'stars' last so long is because...)
Smoking (slight decrease in amount of open arteries!)
Rrecent LARGE meal
There are many more...
wont bore you with them!